Transcription

2 Covalent Bonds Covalent bond: bond in which one or more pairs of electrons are shared by two atoms. Covalent bonding occurs when two (or more) elements share electrons. This most commonly occurs when two nonmetals bond together. Because both of the nonmetals will want to gain electrons, the elements involved will share electrons in an effort to fill their valence shells.

3 Such bonds lead to stable molecules if they share electrons in such a way as to create a noble gas configuration for each atom. Diamond is strong because it involves a vast network of covalent bonds between the carbon atoms in the diamond.

4 Diamond Carbon has four electrons in its valence shell (outershell). Since this energy shell can hold eight electrons, each carbon atom can share electrons with up to four different atoms.

5 Carbon alone forms the familiar substances graphite and diamond. Both are made only of carbon atoms. Graphite is very soft and slippery. Diamond is the hardest substance known to man.

6 Carbon atoms in diamond are covalently bonded and are arranged in a three-dimensional tetrahedral structure. In this rigid network, none of the carbon atoms can move. This accounts for the fact that diamonds are so hard and have such a high melting point.

7 Diamond is the purest form of natural carbon. It occurs as small crystals embedded in rocks. These are supposed to have been formed by the crystallization of carbon under extreme pressure and temperature in the interior of the earth.

8 Nowadays, synthetic industrial diamonds are being manufactured by subjecting graphite to very high temperatures and pressures. Carbon atoms in diamond have tetrahedral structure. Each atom of carbon is surrounded by four other atoms that together forms the tetrahedral structure.

9 1. Diamond is chemically very inert. 2. It does not react with any substance at ordinary temperatures. 3. When heated in oxygen to about 800 o C, it completely burns to form carbon dioxide. 4. This shows that diamond is pure form of carbon.

10 A good example of a covalent bond is that which occurs between two hydrogen atoms. Atoms of hydrogen (H) have one valence electron in their first electron shell. Since the capacity of this shell is two electrons, each hydrogen atom will "want" to pick up a second electron.

11 In an effort to pick up a second electron, hydrogen atoms will react with nearby hydrogen (H) atoms to form the compound H 2. In this way, both atoms share the stability of a full valence shell.

12 Because the hydrogen compound is a combination of equally matched atoms, the atoms will share each other's single electron, forming one covalent bond.

13

14 Covalent bond

15 Polar and Nonpolar Covalent Bonding: There are, in fact, two subtypes of covalent bonds. Polar and Nonpolar Covalent Bonding

16 Nonpolar covalent bond The H 2 molecule is a good example of the first type of covalent bond, the nonpolar bond. Because both atoms in the H 2 molecule have an equal attraction (or affinity) for electrons, the bonding electrons are equally shared by the two atoms, and a nonpolar covalent bond is formed.

17 Polar covalent bond A polar bond is formed when electrons are unequally shared between two atoms. Polar covalent bonding occurs because one atom has a stronger affinity for electrons than the other (yet not enough to pull the electrons away completely and form an ion).

18 In a polar covalent bond, the bonding electrons will spend a greater amount of time around the atom that has the stronger affinity for electrons. A good example of a polar covalent bond is the hydrogen-oxygen bond in the water molecule. Oxygen is much more electronegative than hydrogen, and so the electrons involved in bonding the water molecule spend more time there.

19 The primary difference between the H-O bond in water and the H-H bond is the degree of electron sharing. The large oxygen atom has a stronger affinity for electrons than the small hydrogen atoms. Because oxygen has a stronger pull on the bonding electrons, it preoccupies their time, and this leads to unequal sharing and the formation of a polar covalent bond.

20 Polar covalent bonding simulated in water

21 Ionic Bond Ionic bond: bond in which one or more electrons from one atom are removed and attached to another atom, resulting in positive and negative ions which attract each other. If one or more atoms lose electrons and other atoms gain them in order to produce a noble gas electron configuration, the bond is called an ionic bond.

22

23 Typical of ionic bonds are those in the alkali halides such as sodium chloride, NaCl. Chlorine is in a group of elements having seven electrons in their outer shells. Members of this group tend to gain one electron, acquiring a charge of -1. Sodium is in another group with elements having one electron in their outer shells. Members of this group tend to lose that outer electron, acquiring a charge of +1. Oppositely charged ions are attracted to each other, thus chlorine Cl- and sodium Na+ form an ionic bond, becoming the molecule sodium chloride.

24 Ionic bonds generally form between elements in: Group I (having one electron in their outer shell) and Group VIIa (having seven electrons in their outer shell). Such bonds are relatively weak, and tend to disassociate in water, producing solutions that have both Na and Cl ions.

26 Hydrogen Bond. The fact that the oxygen end of a water molecule is negatively charged and the hydrogen end positively charged means that the hydrogens of one water molecule attract the oxygen of its neighbor and vice versa. This is because unlike charges attract each other.

27 This largely electrostatic attraction is called a hydrogen bond and is important in determining many important properties of water that make it such an important liquid for living things. Water can also form this type of bond with other polar molecules or ions such as hydrogen or sodium ions.

28 Hydrogen Bonds Polar molecules, such as water molecules, have a weak, partial negative charge at one region of the molecule (the oxygen atom in water) and a partial positive charge elsewhere (the hydrogen atoms in water). Thus when water molecules are close together, their positive and negative regions are attracted to the oppositelycharged regions of nearby molecules. The force of attraction, shown here as a dotted line, is called a hydrogen bond. Each water molecule is hydrogen bonded to four others.

29

30 This picture represents a small group of water molecules. Hydrogen bonds between unlike charges are shown as lines without arrows on the ends. The double arrowed lines represent the fact that like charges repell each other. Both hydrogen bonds and the repelling forces balance each other and are both are important in determining the properties of water.

31 Hydrogen Bonding Hydrogen bonding differs from other uses of the word "bond" since it is a force of attraction between a hydrogen atom in one molecule and a small atom of high electronegativity in another molecule. That is, it is an intermolecular force, not an intramolecular force as in the common use of the word bond. Hydrogen bonding has a very important effect on the properties of water and ice.

32 The hydrogen bonds that form between water molecules account for some of the essential - and unique - properties of water: The attraction created by hydrogen bonds keeps water liquid over a wider range of temperature than is found for any other molecule The energy required to break multiple hydrogen bonds causes water to have a high heat of vaporization; that is, a large amount of energy is needed to convert liquid water, to water vapor.

33 Metallic Bonds The properties of metals suggest that their atoms possess strong bonds, yet the ease of conduction of heat and electricity suggest that electrons can move freely in all directions in a metal. Not important in soils.

34 van der Waals bonds The attractive forces between molecules in a liquid can be characterized as van der Waals bonds. Van der Waals bonding is important in minerals such as: graphite and clay minerals (Van der Waals bonds may be a major source of cohesion in fine grained soils).

35 the van der Waals force, named after Dutch scientist Johannes Diderik van der Waals is the attractive or repulsive force between molecules (or between parts of the same molecule) other than those due to covalent bonds or to the electrostatic interaction of ions with one another or with neutral molecules.

36 Van der Waals bonds Neutral molecules may be held together by a weak electric force known as the van der Waals bond. It results from the distortion of a molecule so that a small positive charge develops on one end and a corresponding negative charge develops on the other.

37 A similar effect is induced in neighbouring molecules, and this dipole effect propagates throughout the entire structure. An attractive force is then formed between oppositely charged ends of the dipoles. Van der Waals bonding is common in gases and organic liquids and solids.

Most atoms are not Packet 4: Bonding Atoms will, or share electrons in order to achieve a stable. Octet means that the atom has in its level. If an atom achieves a stable octet it will have the same electron

Answer the following questions. CHEMISTRY BONDING REVIEW 1. What are the three kinds of bonds which can form between atoms? The three types of Bonds are Covalent, Ionic and Metallic. Name Date Block 2.

Chapter 2 The Chemical Context of Life Multiple-Choice Questions 1) About 25 of the 92 natural elements are known to be essential to life. Which four of these 25 elements make up approximately 96% of living

Name Date lass APTER 6 REVIEW hemical Bonding SETIN 1 SRT ANSWER Answer the following questions in the space provided. 1. a A chemical bond between atoms results from the attraction between the valence

Most of the matter around you and inside of you is in the form of compounds. For example, your body is about 80 percent water. You learned in the last unit that water, H 2 O, is made up of hydrogen and

Chemistry I ATOMIC BONDING PRACTICE QUIZ Mr. Scott Select the best answer. 1) A mutual electrical attraction between the nuclei and valence electrons of different atoms that binds the atoms together is

5. Structure, Geometry, and Polarity of Molecules What you will accomplish in this experiment This experiment will give you an opportunity to draw Lewis structures of covalent compounds, then use those

Chapter 13 - LIQUIDS AND SOLIDS Problems to try at end of chapter: Answers in Appendix I: 1,3,5,7b,9b,15,17,23,25,29,31,33,45,49,51,53,61 13.1 Properties of Liquids 1. Liquids take the shape of their container,

The Nature of Molecules Chapter 2 Energy and Metabolism Chapter 6 Chemical Bonds Molecules are groups of atoms held together in a stable association. Compounds are molecules containing more than one type

Chapter 6, Section 2 Key Concept: Chemical bonds hold compounds together. BEFORE, you learned Elements combine to form compounds Electrons are located in a cloud around the nucleus Atoms can lose or gain

CHAPTER EIGHT BNDING: GENERAL CNCEPT or Review 1. Electronegativity is the ability of an atom in a molecule to attract electrons to itself. Electronegativity is a bonding term. Electron affinity is the

1. If the electronegativity difference between the elements in compound NaX is 2.1, what is element X? bromine fluorine chlorine oxygen 2. Which bond has the greatest degree of ionic character? H Cl Cl

Minerals in granite The igneous rock granite is composed of many separate grains of several main minerals Figure 2.1 What is a mineral? Naturally occurring solid Specific chemical composition Crystal structure

Bonds hapter 8 Bonding: General oncepts Forces that hold groups of atoms together and make them function as a unit. Bond Energy Bond Length It is the energy required to break a bond. The distance where

CHAPTER 1 2 Ionic Bonds SECTION Chemical Bonding BEFORE YOU READ After you read this section, you should be able to answer these questions: What is ionic bonding? What happens to atoms that gain or lose

Q. Hydrogen chloride (HCl) can be made by the reaction of hydrogen (H 2) with chlorine (Cl 2). (a) The diagrams represent molecules of hydrogen and chlorine. Draw a similar diagram to represent a molecule

S block elements p block elements and chemical bonding -1 1.Group I elements do not occur free (native state) in the nature because a. They are unstable b. Their compounds with other elements are highly

Name: Date: 1. Which of the following best describes an atom? A. protons and electrons grouped together in a random pattern B. protons and electrons grouped together in an alternating pattern C. a core

1. Atoms of elements that are in the same group have the same number of 5. Mendeleev left gaps in his periodic table because A. Protons B. Valence Electrons A. the table was too full B. no known elements

Chapter 5 TEST: The Periodic Table name HPS # date: Multiple Choice Identify the choice that best completes the statement or answers the question. 1. The order of elements in the periodic table is based

Name: Exam 2 Chemistry 65 Summer 2015 Score: Instructions: Clearly circle the one best answer 1. Valence electrons are electrons located A) in the outermost energy level of an atom. B) in the nucleus of

Part B 2 Allow a total of 15 credits for this part. The student must answer all questions in this part. 51 [1] Allow 1 credit for 3 Mg(s) N 2 (g) Mg 3 N 2 (s). Allow credit even if the coefficient 1 is

ATOMS AND BONDS Atoms of elements are the simplest units of organization in the natural world. Atoms consist of protons (positive charge), neutrons (neutral charge) and electrons (negative charge). The

7.4 Using the Bohr Theory LEARNING TIP Models such as Figures 1 to 4, on pages 218 and 219, help you visualize scientific explanations. As you examine Figures 1 to 4, look back and forth between the diagrams

1. Each element has its own characteristic atom in which a. the atomic mass is constant. b. the atomic number is constant. c. the mass number is constant. d. two of the above are correct. e. all of the

Chapter 2: Atoms, Molecules & Life What Are Atoms? An atom are the smallest unit of matter. Atoms are composed of Electrons = negatively charged particles. Neutrons = particles with no charge (neutral).

Section 4 4 bjectives After this lesson, students will be able to L.1.4.1 State what holds covalently bonded s together. L.1.4.2 Identify the properties of molecular compounds. L.1.4.3 Explain how unequal

9.2 Network Covalent, Ionic, and Metallic Solids YOU ARE EXPECTED TO BE ABLE TO: Classify non-molecular solids as either network covalent solids, ionic solids, or metallic solids. Relate the physical properties

ANSWER KEY Energy Levels, Electrons and IONIC Bonding It s all about the Give and Take! From American Chemical Society Middle School Chemistry Unit: Chapter 4 Content Statements: Distinguish the difference

Science of Kriyayoga IST 111-01, Spring 2005 Matter, Elements, Compounds, Chemical Bonds and Energy In our discussion so far, we have discussed human nervous system and cell biology, in addition to the

LS1a Fall 2014 Section Week #1 I. Valence Electrons and Bonding The number of valence (outer shell) electrons in an atom determines how many bonds it can form. Knowing the number of valence electrons present

COVALENT BOND VS IONIC BOND You have seen how elements are similar to us and as you know them closely you will find some more similarities to our behaviour. You must have experienced the law of attraction

First, what is a covalent bond? Get Your Forces Right! Covalent Bond Definition: The sharing of a pair of electrons through orbital overlap. Some examples: Methane, CH4 Cyclohexane, C6H12 Covalent bonds

Introduction Laboratory 11: Molecular Compounds and Lewis Structures Molecular compounds are formed by sharing electrons between non-metal atoms. A useful theory for understanding the formation of molecular

Chapter 18: How Atoms Bond and Molecules Attract Name: 18.1: Electron-Dot Structures Help Us to Understand Bonding What are the 3 types of bonds we will be learning about? When 2 atoms meet, which part

4.5 Physical Properties: Solubility When a solid, liquid or gaseous solute is placed in a solvent and it seems to disappear, mix or become part of the solvent, we say that it dissolved. The solute is said

5s Solubility & Conductivity OBJECTIVES To explore the relationship between the structures of common household substances and the kinds of solvents in which they dissolve. To demonstrate the ionic nature

The Periodic Table and Atomic Properties The periodic table originally came from the observation that when the elements are arranged by atomic mass, properties recur periodically. (Mendeleev) Now we understand

Basic Chemistry Why do we study chemistry in a biology course? All living organisms are composed of chemicals. To understand life, we must understand the structure, function, and properties of the chemicals

Lab 5: Periodic Trends Part I: (Prelab) A Computer Study and Introduction to ChemDraw Part II: Acid-Base Properties of Period 3 and Group 5A Elemental Oxides Part III: Oxidizing Ability of the Elemental

Date: Science 10 4.1 Atomic Theory & Bonding What is an Atom? smallest particle of an element that still has the properties of that element An atom = proton(s) + electron(s) + neutron(s) (PEN) Fun Fact:

EXPERIMENT 9 Dot Structures and Geometries of Molecules INTRODUCTION Lewis dot structures are our first tier in drawing molecules and representing bonds between the atoms. The method was first published

SCH4U UNIT TEST Atomic & Molecular Structure Name: _ Date: Part A - Multiple Choice Identify the letter of the choice that best completes the statement or answers the question. 1. Who postulated that electrons

BOND TYPES: THE CLASSIFICATION OF SUBSTANCES Every (pure) substance has a unique set of intrinsic properties which distinguishes it from all other substances. What inferences, if any can be made from a

Periodic Table Instructional Background Patterns in Element Properties (History): Elements vary widely in their properties, but in an orderly way. In 1869, the Russian chemist Dmitri Mendeleev produced

Section 8.5 Objectives Describe how electronegativity is used to determine bond type. Compare and contrast polar and nonpolar covalent bonds and polar and nonpolar molecules. Generalize about the characteristics

Atomic Structure Atoms and elements Everything in the world is made up from about 100 elements. Every element is made up of very small particles called atoms. An element is a substance in which all the